Expansible rotary drill bit and cutter



July 7, 1953 u. n. BAKER mustan Rp'rmv mm, 11' CUTTER Filed; Sept... 26. 1-949 2 Sheets-Shed. 1

INVENTOR.

flrroelvsys y 7, 1953 J. R. BAKER I 2,644,673

EXPANSIBLE ROTARY DRILL BIT AND CUTTER.

Filed Sept. 26; 1949 zsheets-sneet 2- 4s .z-fomv 1Q. BAKER,

. INVENTOR.

4 44 39 gay Patented July 7, 1953 UNITED STATES PATENT OFFICE j V l 1 2,644,673

' EXPANSIBLE ROTARY DRILL BIT AND CUTTER John E. Baker, Pasadena, Calif.,-assignor to Baker Oil Tools, Inc., Vernon, Califl, a. corporation of California I Application September 26, 1949, Serial No; 117,771

The present invention relates to drill bits, and

more particularly to bits having one or more cutters movable between retracted and expanded positions.

Rotary drill bits of the drag type are known operation in a well bore; for enlarging the diameter of well bores below Fig, 2 is a side elevation, partly in section, of a casing string. These bits may include one or the drill bit shown in Fig. 1; o more cutters or'blades mounted on the bit body Fig. 3 is a cross-section taken along the line initially in retracted position, the blades being 3 3 on Fig. 1; I expanded outwardly when disposed below the Fig. 4 is a front elevation, on an enlarged scale, lower end of the casing string to increase the well of the leading face of one of the cutter blades; bore diameter upon rotation of the drill bit. Fig. 5 is afront elevation of another cutter Hardfacing materials may be applied to the blade that can be used in a rotary drill bit of blades, after which the hardfaced blades are heat the type disclosed in Fig. 1; treated. These operations result in the 'format Fig. 6 is an enlarged fragmentary section taken tion of small cracks in the hardfaced surfaces of along the line '66 of Fig. 4'. the'blades, which are often the source of fatique Underreamers of the type disclosed in the draw and other types of failures. Former shapes of ings are described in detail in United States blades have also contributed ,to blade failure as Patent No. 1,857,616. They include an elongate the result of the concentration of the loads immain supporting body I0 provided with an upper posed upon the blades. Moreover, the cutter threaded'box II- attachable to the lower end of a blades do not operate smoothly in certain formastring of drill pipe l2 or the like, by means of tions, and may-have sudden shock loads imposed which the underreamer is lowered in the well bore upon them during their rotation in thewell bore. and rotated in-the performance of its underream- Accordingly, it is an object of the presentining operation. The body has a central longivention to improve cutter blades of the-drag type tudinal passage I3 therethrough, merging into employed in expansible rotary drill bits. diametrically opposed elongate slots 14 opening Another object of the invention is to minimize outwardly of the body. A pair of cutter blades the presence of cracks in the surfaces of rotary ii of the drag type are movable'within the slots, drill bit blades which are hardfaced. being mounted upon a hinge pin 16 extending 1 A further object of the invention isto provide throughthe bodyand across itspassage I3. a cutter blade for anexpansible rotary drill bit -The cutters l5 have an initial downward posiwhich is more flexible than blades heretofore used, tion substantially completely retracted within the and which has better shock resistance. confines of the body l0, and are Swingable u Still another object of the invention is to dis- Wardly in opposite directions to extend beyond tribute the load imposed on the cutter blade over the periphery ofthe body, occupying a generally a substantially larger portion of the blade. horizontal position, with their upper sides l5a'en-' -Yet a further object of the invention is to p'roagin t upper shoulders I! of the longitudinal vide an expansible rotary drill bit, embodying slots l4. A second set of longitudinal slots [8 blades that operate smoothly -in enlarging the extend upwa d y to One Side Of and above-the diameter of the well bore. 7 40 stop shoulders 11 at the ends of the main slots, Another object of the invention isto provide to pr v e passages thr h w ich rilli fluid an expan'sible drill bit embodying cutter blades y p s fordis har e Onto the cutter blades l5. that tend to keep the bit centered in the .well bore. The blades are swingable inwardly and. out- This'invention possesses many other advan- Wardly of the body slots I4 in response to uptages, and has other objects which may-be made Ward and-downward movement of an operating more clearly apparent from a consideration of a P unger, I 9 slidable within the central pass form in which it maybe embodied. This form l3 of; themain bo y- Thisplun er in lu e a is shown in the drawings accompanying and tubular plunger body 20 having a transverse hole forming part of thepresent specification. It will hroughd pendins. le s 2| in its lower end for now be described in detail,.for the purpose of receivin pivot p ,1 which upper d illustrating the general principles of the 'invenof a pair of links 3 are p votally m unted be: tion;-but it is to be understood that such detailed tweenthe legs. The lower end of each link is description is not to be taken in a limiting sense, pivotally attached to;a cutter blade [5 by means since the scope of the invention isbest defined of a pin '24 It is to be'noted that the links 23 by the appended claims. are pivoted to the blades on opposite sides of 5 Claims. (01. 25576) Referring to the drawings:

expansible rotary drill bit or rotary underreamer, with its cutter blades in expanded position for tioned, until the blades occupy horizontal positions in contact with the body shoulders I1.

The upper end of the body passage I3 is enlarged in diameter to form a cylinder 25 slidably receiving the upper piston portion 26 of the plunger, which is also enlarged to a diameter greater than the lower plunger body portion 20. A plurality of piston rings-21, of-rubber or similar material, are mounted on the piston for slidable sealing engagement with the wall of the cylinder to prevent leakagein both'directions around the piston. smaller diameter plunger body portion 20, one, end engaging the lower end 92 of the cylinder and its other end engaging the piston 26. This spring is under compression and tends to elevate the plunger 19 and retract and maintain the blades l5 in their inward position within the confines of the body [0.

The plunger I9 is movable downwardly and the blades expanded outwardly by the. pressure of fluid, like drilling mud, pumped'downwardly through the string of drill pipe I2, and acting upon the piston 26. Since ,it is desired to discharge the drilling fluid onto the cutters l5 to maintain them free of detritus, the fluid continues downwardly through a central passage in the plunger l9 for discharge in opposite A spring 28 encircles the.

4 upper wall 4| of this recess may be generally parallel to the inclined lower edge 35. The upper edge I5a may also be provided with a similar recess extending from the outer edge 36 inwardly towards the body I 0.

Hardfacing material is welded to the parent metal of each blade within the recess 40. Such hardfacing; material may include peas? or particles of tungsten carbide 42 that may be placed in two rows 43, 44, one above the other and substantially at right angles to the inclined cutting edge-35ofthe blade. As an example, each pea may be about g-inch by /4-inch by 1-inch and they may be placed in the recess spaced about /3115101'1 apart. The upper row 43 may be stagered- With respect to the lower row 44. These peas 42 are welded within the recess 40 to the parent metal of the blade by the use of a welding rod which is preferably in the form of a tube containing tungsten carbide of a suitable mesh (say eight to thirty mesh). This tube .of tungsten carbide is applied between and over the peas 42 until substantially the entire recess 40 has been filled. Thereafter, if desired, another layer of suitable welding material can then be applied over the peas 42 and finer mesh tungsten car-. bide 45,for the purpose of filling any porosity that may remain afterthe tube rod has been used.

The ,hardfacing material may be applied in the recess 40 running alongthe lower inclined cutting edge 35, along the outer edge 36 ,and

directions through elongate slots 3| in the lower portion of the plunger body, and through the upper body slots l8 onto the forward cutting faces of the cutter blades. In. View of this dis- I charge of fluid, an orifice or restriction 32 is provided in the plunger passage 30 to enable a back pressure to be built up on the high pressure side of the piston 26, sufiicient in value to overcome the compressive force of the spring 28, shift the plunger [9 downwardly, and swing the blades l5 outwardly, through the agency of the pin and link connections 22, 23,25 between the plunger 19 and blades 15.

From the drawings, it is to be noted that each cutter blade 15 has a lower cutting edge 35 that is inclined in an upward and outward direction when the blade is expanded to its horizontal position. When in this position, the outer edge 36 of the blade has a substantial longitudinal extent; so as to have adequate bearing against the formation wall. i

The lower inclined edge 35 extends from a point B; adjacent the bit body Ill to the outer edge, 36 of the blade, and preierablymakes-a substantial angle with the horizontal. an example, the angle may be forty degrees, although wide. variations from this angular extent can be made, depending upon the length of the blade in a horizontal direction. Assuming that the blade is quite long so as to greatly enlarge the well bore diameter, the angle which the lower inclined edge makes withithehorizontal'will be less. As an example, a. lesser angle is obtained ,if blades-are used tht extend horizontally "outwardly eighteen inches from the pivotalaxis aboutthe pin [6. Y 1

Each blade has a flat leadingface-S'i and-also a flat trailing face 38. The lower inclined edge 39 of the trailing face is beveled, terminatingat the lower end of a recess 40 formed along the inclined leading edge 35 and extending from the the outer edge 36 to approximately the point B along the blade within the body slot l4. The

also along the upper cutting edge l5a. After its application, the leading face 31 of the blademay be suitably ground to present a smooth surface and to insure proper swinging movement-ofthe blade about the pivot pin 16 during its shifting between retracted and expanded positions.

The sheath of hardfacing-materialsapplied to the blade has a different thermal coeflicientof expansion than that of the parent blade metal. As a result, cracks 50 in the hardfacing appear after the blades are finish ground. These-cracks apparently occur during the, hardfacing operation, or during the subsequentheat treatment, to which the blades are; subjected. These cracks are usually normal to the:cutting edge-35 and are points of stress concentration, despite, the fact that they may or maynot originally pence trate into the parent-metal; These cracks also appear in the hardfacingq material at. the point R in the b-ladelying near-or within. itheibody' slot I4. 1 7

After the expansible drill bit has been lowered in the well bore to a'pointbelow the casing string at which the hole enlarging operation-is to take place, the pumps at, the-top ofthewell bore are started and the string of drill pipe-l2 and drill bit are rotated at the proper-speed..- Pressure. of the fluid on thepiston 26urges the latter downwardly and swings'thelblades l 5 inop pos-ite directions outwardly about the hinge;- pin IS. .The upper edges 15a, of the blades first engage the formation and begin, enlargingthe hole. Eventually, the bladeshave been expanded outwardly totheir horizontal position, whereupon drilling weight may be imposedronthe drill;

I stringand bit tocause the lower'leading edge ,-3 5

to form a frusto-conical shoulder Sl the. formation, the inclination of the. shoulder being essentially the same as the degree of inclination of the leading edge 35 to thebitand hole axis. The proper drilling "weight is applied to the tool during its rotation, the fluid exiting from the tool to maintainits blades free of cuttings and to carry the cuttings upwardly around the drillpipe l2 to the topof the well bore.

.-'.-Each.blade l5 isactually in the nature of a cantilever beam, the greatest bending moment on'..the blade being at the. point, or along the line, where the blade enters. the body, orat the periphery. of the bodyxlll.v j 5 Blades can beused havinglower cutting edges 35a :disposed substantially at right angles to the axis of the bit body (seeFi'g. 5). The recess in which the hardfacing materials 42.,I45are applied are also disposed along this lower edge and extend partly into the bit body. The cracks developed as the result of applying the hard-.- facing material, and the subsequent heat treatment, are, disposed at right. angles to the lower cuttingedge. 3511, or generally parallel to the axis of the bit. These'cracks also are onthe blade portion disposed within the body, since the .hardfacingrmaterial extends part way into the body slot I4. Such blades formed a shoulder Sia ingthewell bore that '-'is normal to the bit axis. As a result, substantially all. of the load imposed on each cutter blade is concentrated along its lower cutting elge 5la and is transmitted to the body of the bit at the point .R where the edge enters thebody slot 14, At this point, the bendingmomen'tand shear stresses are the greatest. The parent metal of the blade is of reduced diameter section atthisa-p'oint of stres's'concentration, because of the provision of the recess 40, and thecrack or cracks 5 in the hardfacing material at this point, which may or may not initially extend into the parent metal, form loci where blade failure can occur. I

operation of the blades upon the formation shoulder {Ha -imposes severe shock loads on the blades, resulting in blade failure, usuallyat the point R, where the blades enter the body It.

Thus, the 1 blades of the design shown in Fig. 5 have the reactive drilling torque imposed thereon in a direction generally in line with the hardfacing cracks 50. trated in the blade along its lower cutting portion 35a. The remainder of the blade contributes very little to withstanding the stresses to which the blade is subjected. In addition, the generally rectangular shape of the blade makes the blade comparatively rigid and nonfiexible, rendering it less able to withstand shock loads imposed upon it.

As distinguished from the generally rectangular blades, applicant provides his hardfacing material 42, 45 along an inclined lower cutting edge 35. The hardfacing peas 42 are disposed normal to this lower edge, which also results in the cracks 50 extending normal to this inclined edge. The blade forms an inclined shoulder 51 in the formation, and not merely a shoulder at right angles to the axis of the bit body. As a result, the reactive torque imposed upon each blade is not transmitted to the body merely at a comparatively small locust R where the lower portion of the blade enters the body, but is transmitted throughout a substantial longitudinal extent of the blade to the body. By referring to Fig. 4, it becomes evident that the reactive torque imposed on the cutter blade l5 during its drilling of the inclined formation shoulder 5| is' transmitted along a substantial length S of the blade, which may extend generally between the broken lines 60, this torque being transmitted along substantially the entire length of the blade to the bit body 10. I

Thus, the reactive torque is not localized at a Rotation of the bit and This torque is c0ncen-' said blad on said body;v

comparatively small .point (as: R); where -.h'ard-.- facing cracks, or deep hardening. cracks resulting from heat treatment, may be present, .and where the iparent'metal of theblade. has a-lesser section; The blade can, thereforabe subj ectedtosubstantially greater loads. without danger of its failure, especiallyat the point of greateststress concentration adjacent the periphery of the bit body. In addition, the blade is not proneto failure f at any. of'the othercracks along itslower edge 35, since-the forces associated. with'the torque being transmitted do not coincide with. or act parallel to the cracks, cutting diagonally across them. i 1

,By tapering the cutting edge 35 of,.the:blade, the blade is made more flexible than a straight blade, because the blade-substantially directly in proportionto the bending moment imposed upon-it. -Since the blade is more flexible, it 'has better shock resistance than a straight; blade (as in Fig.-.5),-.:and-. is

less susceptible to breaking when sudden shock loads are imposed uponit. As a matter offfact, the inclination of the blade reducesthe imposis tion of shock loads 35 attacks any hard shells, or other hardformations, from a point T closerto the bit body,-the edges 35 gradually workingout on :the shellt'o theouter edge 36 of the-blade: straight lower-edges (Fig; 5.) at right angles to the bit body contact such hard shells at the outer ends 36a of the. blades first, :wherethe, moment arm is greatest and where the shock loads. have the maximum effect. upon the blade at its .point R;of greateststress concentration adjacent the periphery of the bit body 10; i: l I Not only do the tapered blades minimize the opportunities for imposing shock loads 011 13118 blades, but, they also resultin the formation of a downward and inwardly inclined shoulderjl on the formation for as making it run smoother. The inventor claims:

, 1. In an expansible rotary drill bit: a main body; a cutter blade; means pivotally mounting means for swinging said blade between a retracted position'substantially entirely within said body and an expanded posi-'- tion extending substantially outwardly of said body; said blade having a lower cutting portion providing a lower edge continuously inclined substantially to the body axis in a downward and inward direction when the blade is in expanded position; said inclined portion having a recess formed in the leading .face of the blade and extending upwardly from said lower edge and also extending from a point adjacent said body to the outer edge of the blade; and hardfacingelements in said recess welded-to said blade, said elements being arranged substantially normal to the lower inclined edge of said blade.

2. In an expansible rotary drill bit: a main body; a cutter blade; means pivotally mounting said blade on said body; means for swinging said blade between a retracted position substantially entirely within said body and an expanded position extending substantially outwardly of said body; said blad having a lower cutting portion providing a lower edge continuously inclined substantially to th body axis in a downward and inward direction when the blade is in expanded position; said inclined portion having a recess formed in the leading V extending upwardly from said edge and also its section modulus varies across uponit, since the taperede'dge Blades having 1 cooperation '.with" the face of the blade and I each :ofisaidposition;

eiztendingzfrom: aepoint ziadjacent said, :body: to V body havingza longitudinal 1 slot; ta'pair of fcutterblades in.:said slot; means .pivotallysmounting said 'blades onsaid body; a means for swinging. said blades in r opposite idirections=-between. retracted positions substantially entirely within saidu'bo'dy slotcandl-texpanded positionsextending'in opposite directions substantially: outwardly of saidrbody;

blades: having: a :lower cutting: portiozr :providing :a' lower "edge continuously inclined substantially to the .body axis :inar'downward; and inward direction when the blade is. in expanded said. inclined.. portion1 having: recess formed; in: the leading. face of the blade and extendingiupwardly' fromsaidrlower edgeand also extending :from: as point adjacent :said::body: slot tmtheouter edgezoflthezblade; hardfacing elementsein said: recess weldedltolsaidxblade 7 said elements: beinglarrangedisubstantiallylnormal to thee-lower inclined edgesofisaid blade.-

4: A fiat,; elongate cutter blade :for :an Eexpan sible-crotarys drillebit having-a hole therein for mountingrisaid ..blade';.on1a; bit body, said blade having; as lower; cuttinge portion: of extended lengthlprovidin'g: aelower. edge continuously inclined-Yin an-downward andinward direction from the outer portion; of said'blade toward the inner portion of said blade; saidinclined portion have ing arecess formed in' the leading face of the blade' and extending upwardly from said lower edge and. also extending-from'the'outer edge of the blade 'inwardly a' substantial distance toward the bladeihol;.andihardfacing selements in said recess welded to said-;bl'ade',; said elements-:being arranged: substantially normal to thei lower-21inclined eclgeeofrsaid:blade-1v 5. man expansiblerotary drill.v bitiz; aamain body: a cutter: blade :meanse 'pivotally 'zmountin said blade on said body; means 'for-.swinging:said blade between? af retracted position wsubstantially entirely WithilliSfiid zbody 'andtaniexpan'dedipos'i tion; extending substantially? outwardly; or said body: .said blade having:;a 1 lowerzrcuttingzportin providingza lower ed er-continuouslyt inclined$ubz stantially to the :bo'dyr; axis :in "a downward and inward directioncwhen' the-zblade eis .in-zexpamied position; .saideinclined portion: having-2a recess formed in thexlea'ding iacesofsthetblade :an'd iexz-z tending npwardlyifroml said lower edgezand ta-lso extending .froma .pointsadjacent said bodyltoethe outerredgeof said;.blade; hardfacing zelements iin said recess; said elements being -arranged; sube stantiallyl normal .to the; lower." inclined; edgerof said-blade; and handfacing materialweldingtsaid elements ltotsaidbladeinsaidzrecess; r

Jenna; BAKER-e.

References Cited in tlie file. of L thispatent...

UNITED: STATES;.-PA!I'ENTS:

' Gascoigne' Dec. 

